[Yellow oat grass intoxication in horses: Pitfalls by producing hay from extensive landscapes? A case report]

Vitamin-D intoxication by yellow oat grass is often reported under the syndrome of enzootic calcinosis in ruminants in the upper regions of the Alps. The intake of Trisetum flavescens in ruminants and horses induces calcification of soft tissue, including vessels, tendons and ligaments, lung, heart and kidneys. Clinical symptoms, including a reluctance to move, inappetence, body-weight loss and impaired organ function, are frequently observed. To date, there are only a very few case reports about yellow-oat-grass intoxication in horses. The present case report describes Vitamin-D intoxication by yellow oat grass in a riding stable in Thuringia, Germany. The horses, which were fed hay with a 50% contamination of Trisetum flavescens, displayed symptoms, including inappetence, body-weight loss, colic, polydipsia and polyuria. The hay, contaminated with Trisetum flavescens, was harvested from an extensively cultivated landscape according to the European Fauna-Flora-Habitat (FFH)-directive. The present case report demonstrates the pitfalls in producing hay from extensively used landscapes and indicates some peculiarities of Vitamin-D metabolism in horses.